Communications between endpoints of packet-switched networks may be characterized as flows of associated packets. A particular flow may include packets containing information (e.g., within headers of the packets) that distinguishes the packets from packets associated with other flows. Network devices located between endpoints may alter packets associated with a flow and in doing so may potentially obfuscate the flow with which a particular packet is associated from other network devices. Accordingly, there is a need for correlating packets in communications networks.